A typical example of a mobile communication terminal is a mobile phone. A mobile phone generally contains a display portion (e.g. a liquid crystal display (LCD)) to display information such as telephone numbers or an operational state of the phone so that a user can view such information. Also, in a conventional mobile phone, the display portion is driven by a display drive circuit which is operatively coupled to a power supply switch. When the power supply switch is turned ON to supply power to various components of the mobile phone, the display drive circuit continuously and constantly drives the display portion to display information. Also, the display drive circuit only stops driving the display portion when the power supply switch is turned OFF.
Usually, the mobile phone contains a microphone and a speaker which are provided on a handset housing. Also, the display portion is generally provided on the handset housing in an area between the microphone and the speaker. Therefore, when a user holds the mobile phone to the side of his or her face during a telephone conversation, the user cannot see the information that is displayed on the display portion. However, since the display portion is constantly driven by the display drive circuit when the mobile phone is turned ON, the display portion and display drive circuit unnecessarily consume a substantial amount of current.
In order to attempt to solve the problem above, a mobile telephone is disclosed in Japanese Patent Laid-open Publication No. Hei 7-170226. The mobile phone has an ear-piece portion which is located near the speaker of the mobile phone and a pressure sensor which is coupled to the ear-piece portion. When the ear-piece portion is brought into contact with a user's ear during a telephone conversation, the pressure sensor detects the pressure applied by the user's ear on the ear-piece portion and instructs the display drive circuit to stop driving the display portion. However, the pressure sensor is relatively expensive, and thus, incorporating such sensor into the mobile phone substantially increases the cost of the phone and makes the structure of the phone complicated. Also, in order for the pressure sensor to properly turn OFF the display, the ear-piece portion must remain in contact with the user's ear during the entire conversation. However, when the user's ear is slightly removed from the ear-piece portion (e.g. when the volume of the sound being received by the phone is high), the pressure sensor does not detect any pressure, and the display is not turned OFF. Therefore, the phone may still consume power unnecessarily.